Method of converting aldehydes to acids



main Jan.14,'193d 2,027,377

UNITED STATES PATENT QFFIC METHOD OF CONVERTING ALDEHYDES T ACIDS William J. Hale, Midland, Mich.

No Drawing. Application October 28, 1931,

Serial No. 571,281

1:; Claims. (01. zen-.116)

The present invention relates to an improved acetic acid and hydrogen; the removal of the method of converting aliphatic and aromatic hydrogen through combustion only facilitating aldehydes to their corresponding acids. the drift toward acetic acid.

In the past one well known method of prepar- As a result of considerable experimentation 1' mg aliphatic acids consisted in general of a twohave found, as noted above, that aldehydes can stage process involving first the dehydrogenation be converted into the corresponding acid without of alcohol into the corresponding aldehyde by employing the usual method, that is to say utimeans of metallic catalysts, and the-subsequent lizing either oxygen or potentially available oxyoxidation of the aldehyde and hydrogen formed gen. While not confining myself to any state-'- into the corresponding acid and water respecment as to the rationale of the reaction, it is evi- 10 tively. The second stage of the process, that is dent that theprocess involves the hydration of to say the oxidation of the aldehyde to the acid, the aldehyde to the aldehydrol and the subsewas eifect'ed through the agency of an oxygen quent dehydrogenation of this to the acid, as will supplying material, such as copper oxide. appear more fully hereinafter.

i5 'The present invention is based upon the dis- It is to be noted that the inference of the forcovery that aldehydes may be converted into their mation of an intermediate more or less unstable corresponding acids by a process which, in sharp aldehydrol type of compound has many points contradistinction to prior methods, does not inof support. Ramsay & Young (Phil. Trans. volve the utilization of direct oxidizing agents. 1886-1117) first announced the possibility of fly c nsider d th pr sen n v pr s comaldehydrol through a study of heat evolution and p h ds th ydra i n o a yd startin mavolume contraction directly upon mixing acetalterial tothe corresponding aldehydrol and thendehyde ith water, Perkins (Chem. Soc. the immediately subsequent dehydrogenation of 51,816 1887) and Homfray (Chem. 800- r the aldehydrol t0 e esp g acid. The 811435-1905) established the existence of an process i fur h r chara teriz d by in efaldehydrol, specifically ethylidene glycol, and 11- fectuated at a relatively low temperature. In nally Colles (Chem. Soc. 89,1249-1906) actually order to insure success of the operation the conisolated crystals of ethylidene glycol diticns of catalysis should be carefully chosen f and regulated 2) It has been recognized heretofore that when acetic acid, for example, is prepared by the usual process, that is to say by the dehydrogenation of alcohol and the subsequent oxidation of acetaldehyde, considerable portions of the acetaldehyde and hydrogen pass through the oxidation zone unchanged. It has furthermore been observed that this occurs'even in the presence of a large excess of oxidizing material, and even when the 40 temperature of operation is maintained well bei A well known form of chlorinated acetaldehyde is the ordinary chloral hydrate. Evidence has established that here two hydroxyl groups are attached to the same carbon atom.

Further confirmatory evidence of the existence of ethylidene glycol, as well as indications of its particular properties, are found in the study of the action of hydrogen chloride upon acetaldehyde to give ethylidene hydroxy-chloride low the point of incipient complete combustion (CHSCH(OH) c1) 40 of the organic compounds into carbon dioxide r and water. 1 which, upon simply standing at room tempera- As early as 1906 Johaan Walter (D. R. P. lures, loses a molecule of water and passes over 168291) indicates that acetic acid, as well as into u.-a dicmoroethyl-ether 45 acetaldehyde, occurs among the products of ino complete combustion of ethyl alcohol in the pres- (CHacHcl) (clCHCHz) ence of considerable water vapor. It is further- Here it is to be noted t t th tendency for more shown (D. R. P. 185932-1907) that acetic action through the hydroxyl group is actually acid with hydrogen in contact with metals and more pronounced under certain conditions than 50 r u h surfa s in neral yield acetald hyde and the com aratively simple splitting oil of hydrogen water in the neighborhood of 300 C. Walter's chloride and resolution again into original conobservations receivesubstantiation when we constituents. 7 siderthe dehydrogenated ethyl alcohol (that is The fact that an aldehyde can be converted a: the acetaldehyde) interacting with water to yield into its corresponding acid without the utilization of direct oxidizing agents was established by a number of experiments, of which the following is illustrative.

Experiment An ordinary glass combustion tube, properly fitted for intake and outlet of vapors, was filled with pumice upon which was previously precipitated a mixture of 1 part of aluminum hydroxide and 10 parts of cuprlc hydroxide. A current of air was passed through this tube while heated to about 270-300 C. so as to effect a complete oxidation of all the contained oxidizable material. Thereupon oxidation was interrupted and while still held at the stated temperature a cur rent of hydrogen was passed through the tube to effect the complete reduction of all copper oxides into metallic copper and to efl'ectively remove all adsorbed or occluded oxygen from within the porous mass. Several hours time was thus required. Finally the hydrogen was removed from the tube by means of a current of water vapor generated from deaerated water. Into this combustion tube, held at about 250-280 C. was now passed the vapors from a mixture of 44 grams (1 mol.) of pure molecular acetaldehyde and 18 grams (1 mol.) of water. The total eiiluent vapors, requiring about 30 minutes for single passage, were immediately recycled through the tube. At the end of three complete cycles -the products were withdrawn and analyzed as follows. In this analysis allowance was made for the water vapor initially held in the tube.

Grams Acetic acid 1 14.6 Acetaldehyde 33. 0 Hydrogen 0.5 Ethyl acetate 0.2 Water 13.5 C0: and hydrocarbons 0.2

. Total (equals acetaldehyde and water)- 62 Operating according to the procedure described,

the state of equilibrium attained is indicated by the following equation:

o omo +nlo crncoon+m In the closed system in which this experiment is' carried out there occurs a preponderance of acetaldehyde (2 parts-equivalent to 3 mols.) over acetic acid (1 part-equivalent to 1 mol.) in a state of balance. quantitatively, therefore,

we may look upon the reaction as involving 4 mols. of acetaldehyde and 4 mols. of water in the production of 1 mol. of acetic acid and 1 mol. of hydrogen, giving therefore a balanced state between the residual 3 mols. of acetaldelnrde and 3 mols. of water over against 1 mol. of acetic acid and 1 mol. of hydrogen. In other words, in the equilibrium equation above an excess of 3 mols. of acetaldehyde and 3 mols. of

'water is required to drive 1 mol. of acetaldehyde which should result on the conversion of 1 mol. of acetaldehyde out of 4 mols. of this substance into the acid and in the presence of 3 mols. of water extra.

Now the equation, defining the described experiment, requires for equilibrium on the left arm the actual oxidation of acetaldehyde to acetic acid by the addition of elements of water to the carbonyl group, that is the hydration and subsequent removal of 2 hydrogen atoms from the hydrated acetaldehyde or aldehydrol. This is graphically depicted in the following equation:

That this foregoing reaction could be effected so as to secure anything but perceptible quantities of end products in either direction has never been reported. However I have found that, based upon this reaction, an effective process may be developed so that the interaction comes under complete control.

From the foregoing discussion it would appear that the process of producing acid directly from aldehyde without utilizing oxygen or oxygen yielding substances involves only simple hydration and dehydrogenation. In experimentation upon the subject, however, it was found that this was not the case, but that special types of catalysts were required. As pointed out above, metallic copper operated effectively as a. dehydrogenative catalyst. It was noted also that silver, palladium, the platinum metals, and also zinc are effective. However certain other well known dehydrogenative catalysts, such for example as manganous oxide and other metallic oxides, are not effective under the low temperature conditions of the present process. These oxide catalysts do not function until the temperature is raised to approximately 350 C. or above. But even here when they do operate undesired side products are concomitantly produced in such quantities as to discourage their employment. Again, if acetaldehyde and water vapor are passed over metallic copper associated with such pronounced hydrative catalysts as the oxides of tungsten, thorium, titanium, molybdenum, and silicon, at temperatures at or below 350 0., there is little or no production of acetic acid. Above 350 C. hydration becomes apparent, though only slightly and with the undesired accompaniment of high concentration of carbon dioxide.

Similarly the hydrative catalyst aluminum oxide when used alone is not effective; neither is the catalyst manganous oxide. ,Howev'er, when either one of these two catalysts is mixed with metallic copper, and the other conditions of the run are proper-Ly chosen, acetic acid'in relatively large quantities is produced.

Again, certain substances combine the properties of dehydrogenation as well as hydration and at first blush would seem to be well suitedfo'r the present process. Typical examples of such double functioning catalysts are the oxides of zirconium, manganese and cerium. However when acetaldehyde and water vaporsare passed over such oxides alone, at a temperature of 350 or less, no acetic acid is produced. It is only when 'these oxides are associated with the dehydroin fact essential.

- tain catalysts as effective catalytic agents, it was found that only weak base metal hydroxides or oxides were serviceable. It furthermore developed that those elements which form amphoteric hydroxides were particularly useful in the process, but here again only such of these as are able to form basic salts with the organic acids in question, under the conditions of the operation, are serviceable. Finally it was found that only those elements forming amphoteric hydroxides and capable of forming basic salts, which salts resist complete hydrolysis under the action of water uhder 350 C., will serve effectively for the conversion of aldehyde into its corresponding acid.

I have found in short that salts of an organic acid with an amphoteric base, which resist complete hydrolysis under the conditions of operation, are not only particularly well suited but are These substances exert a direct influence upon the conversion. For this reason these ampho'teric basic salts are termed partially hydrolyzable or directive catalysts.

These directive catalysts,.as noted hereinbefore,

are without effect upon the conversion of aldehyde to acid save in the presence of the dehydrogenative catalyst.

A study of the periodic system of elements yields but few metals that satisfy the outlined requirements. These elements are as follows: Group 1, copper; Group 2, beryllium, magnesium and zinc; Group 3, aluminum; Group 4, zirconium and the cerium metals; Group 6, chromium; Group 7, manganese; Group 8, iron and cobalt. In the 8th group nickel was found to-function at the low temperatures employed but it presented a decided tendency toward carbon dioxide formation, and for this reason is not recommended. Iron and cobalt, as well as copper and zinc, are limited to low temperature operations owing to, thehighconcentration of free hydrogen'obtaining, under which the higher temperatures re.- duce their salts to the metallic state.

The necessity for carrying out the present process in the presence of a dehydrogenative catalyst suggested possible aid to be gained by the use of a purely hydrative catalyst. It was found, in conformity with this idea, that the addition" to the catalytic mass of oxides of thorium,- uranium, vanadium, titanium, molybdenum and tungsten, or salts of these elements with known nonvolatile inorganic acids, such as boric and phosphoric acid, did in fact contribute somewhat to the converting effect of the catalytic mass. However, it was found that the presence of these materials except in minuteproportions was in the end disadvantageous because they led to the formation of unsaturated hydrocarbons,- due no doubt to the pronounced. dehydrative effect of these compounds 'upon the aldehyde undergoing treatment. a

It is found, therefore, in general that as to the catalytic conditions of the treatment it is advantageous to employ a catalytic mass rich in dehydrogenative catalysts and containing two or more of the directive catalysts associated therewith. The hydrative effect of the majority of these stated directive catalytic bases contributes to the ready hydrative activity of the mass. The proper proportions for making up such a. consist of approximatelylo molecular equivalents of copper, 1 molecular equivalent each of two directlve catalysts, molecular equivalent of an insoluble salt of a well known hydrative catalyst, such as copper vanadate or tltanate.

It isto be noted, as a further precaution, that insoluble non-hydrolyzable salts of one of the directive bases should not be employed, because by such employment the theoretical total concentration of free hydroxyl group per molecule of catalytic base is lessened. Thus when mani ganous borate (1 mol.) is employed in the place of manganous hydroxide (1 mol.) in association with copper, only about as much acetic acid is formed from the borate in unit time as when the manganous hydroxide is employed. For this reason no doubt we may ascribe the apparent unfitness of certain basic salts of organic acids to their. insolubility.

As has been noted above, the present invention comprises the low temperature conversion of aldehydes to corresponding acids in the presence of certain catalysts and water vapor. The presence of water vapor is highly favorable to the proper practice of the present invention throughout the reaction system. In the first place water vapor affords an excellent means of heat control in the. system to avoid the building up of polymerization products, which latter, it will be noted, are

particularly favored by mineral salts and acids.

is here to be noted that for this reason the inert gases, such as nitrogen'methane and carbon dioxide, may be utilized.

To insure high success of the process it is desirable'that any considerable portions of oxygen be excluded. The presence of readily yieldable oxygen material tends to increase the'formation of carbon dioxide, as obtained in the older methods by making use of a metallic oxide. directly upon the aldehyde for the oxidation of the latter. Forthis reason absolute assurance against the presence of free oxygen or reducibleoxides is recommended and, in the experiment given, was

achieved through the prolonged reduction of the catalytic mass by hydrogen just prior to beginning the operation.

It is also to be noted that the presence of finely divided metals, such as copper, may be detrimental to the present reaction. As is known, the presence of this finely divided metal has a tendency to effect decomposition of acetic acid into methane and carbon dioxide, which decomposition begins in the neighborhood of 260 C. However this decomposition is prevented under the conditions of the present process due to the presence of water vapor. Water vapor very materially repressed this action up to temperatures as high as 350 C. In general the presence of water and material. absence of alkali, and inorganic acid, define here the optimum conditions. The temperature should be maintained generally belo 300 C.

As has been pointed out, the effectiveness and simplicity of the present process depends, in a large measure,'upon the discovery of the beneficial efl'ect of the directivecatalysts. In the preferred form of procedure therefore an amphoteric-hydroxide of a metal, united in part to the organic acid to be produced, is employed. However-the vdroxyl group or one presenting a potentially available hydrogenation unit and thus make possible its interaction with the carbonyl group, In another sense the interaction may be considered as same chemical molecule; and hence when an extensive co-suri'ace with copper is presented an ideal condition is afforded for the rapid dehydrogenation and subsequent hydrolysis into acetic on I. om-orro+mo zomon OH O IV. CH.-0 0M110-COOHa-t-HaOTiCILCO'OH-i-HO-Mn-O-COOH the withdrawal of a molecule of water between the hydrated form of carbonyl and the hydroxyl of the basic metallic organic salt. This possible interpretation of the mechanics of the reaction between basic manganous acetate and aldehyde, for example, is illustrated by the following equation:

The four equations given above comprehend the operative sphere. Thus the invention presents a procedure for the oxidation of aldehydes at the expense of a molecule of water and consequent liberation of the hydrogen formerly com bined in the water. Under the well known prin- Now although the aldehydrol possesses but weakly acetic properties, which is midway between alcohol and acidic acid, nevertheless its great concentration in the reaction zone will considerably favor its interaction with the weak directive catalytic bases, such as hydroxy manganous acetate. A likely result of this interaction is a formation of ethylidene hydroxy manganous acetate. Such type of compound is readily hydrolyzed into its original components as the aldehyde and water pass over the basic manganous acetate and even when a quantity of free acetic acid accompanies the incoming vapors. The action of water therefore operates to prevent the actual building up of the ethylidene manganous v acetate in the system.

is unstable under the operative conditions and i loses a quantity of acetic acid through hydrolysis, this quantity corresponding with the excess in acetic acid over and above that constant quantity held under the conditions of operation to constitute its original basic salt. In the basic salts, that i is the directive catalysts, the aldehydrol type of compound is markedly soluble, thereby offering the possibility of a high concentration of aldehydrate groups for dehydrogenation when such dehydrogenative influence, as is effected by copper,

, can bebrought into play. The mere solution of such aldehydrol in the free acid with abundance of copper present does not afford conditions germane to the conversion of the aldehyde to acid, excepting at much higher temperatures where decomposition is marked. This basic salt therefore plays a valuable role in eflecting a high concentration of aldehydrate-acetate groups within the ciple of equilibrium a shift in the concentration of either the water or the hydrogen may be utilized to control the entire process. In summation, with a catalytic mass of manganous hydroxy acetate and copper there is balanced against it l'mol. of acetaldehyde and '1 mol. of water on one side, and 1 mol. of acetic acid and 1 mol. of hydrogen on the other.

Now it will be observed that the high proportion of acetaldehyde in the end product, as noted in the experiment, is due of course to the presence of hydrogen. In the first experiment operations were carried out in a closed system and no effort was made to displace equilibrium in favor of the formation of acid. However, if we now provide means for withdrawing hydrogen the quantity of acid produced can be increased. Thus by introducing a porous thimble within the reaction zone, the walls of which are permeable substantially only to hydrogen, it becomes a simple matter to remove from 80 to 85% of all hydrogen produced. Such porous thimble may comprise palladium, iron, silica, slllimanite or partially fused earthy material.

In actual operations, therefore, the conditions of the reaction are controlled so as to displace the equilibrium in favor of the production of acetic acid as above stated. A preferred operation is illustrated by the following example.

Example 1A An ordinary combustion tube provided with an inlet and outlet for vapors was filled with about grams of broken pumice previously cleaned and shaken into a mixture of well washed hydroxides of copper, manganese and chromium in minutes and careful calculation ice was then dried in air introduced into the tube and thereafter brought to a temperature of 270-300 C. A stream of oxygen or air was passed through the tube and thereafter a cur-' rent of hydrogen was forced through to displace the oxygen. The flow gas was continued for a sufllcient period of time to completely oxidizethe oxidizable and subsequently reduce the reducible materials contained in the tube.

Vapors of a 20% acetic acid solution were passed through the tube for from 10 to 15 made to ascertain the weight of acetic acid and water remaining within the tube. There was then introduced a mixture of 1 mol. (44 g.) of acetaldehyde and 1 mol. (18 g.) of water in vapor form and the tube was held at temperatures between 260 and 270 C. The vapors issuing from the reaction zone were subjected to dephlegmation and the aldehyde and a portion of the water returned to the system, together with additional quantitles of aldehyde and water. The hydrogen gas for the most part was allowed to escape at the cooler end of the dephlegmator. An analysis of I the liquid product was found to give the following:

Grams Acetic acid (51.5% concentration)..- 15

Acetaldehyde 32 Ethyl aceta .3

Water 14 The process was found to be improved by removing a large portion of the hydrogenas formed from the immediate reaction zone. The conditions of this experiment are given below.

Example. 1.8-

Within a combustion tube-was provided a porous tube, permeable to hydrogen, which porous tube was closed at one end and at the other end the .thimble. .An analysis 'of the liquid product gave the following results:

' v 1 Grams Acetic acid (76.5% concentration) 29.5

Acetaldehyde 22.2

. Water 9 Ethyl acetate v.5

It was ascertained that when operating with an. excess of water vapor an increased yield of acid was secured, as shown by the following example: a

' Example 16 The conditions obtaining in this example were the same as those in 13 with the exception that to the'catalytic mass was added a small amount of copper vanadate. The operations were carried out under such conditions as to insure the. rapid removal of hydrogen from the zone of reaction, and in this run about 1 grams of hydrogen were thus removed. The charge consisted of vapors of arm (1 mol.) ofacetaldehyde and 75154 (3 mob.) of Operating in the manner described a liquid product was secured which analyzed as follows:

"Grams Acetic acid (52.6% concentration) 45 Acetaldehyde v v 11 Water 40.5

It was found that the process was applicable to the conversion ofother aliphatic aldehydes, as shown by the following example:

Example 2.4

mator. Analysis of .the liquid products of conversion showed the following:

Grams N-propiom'c acid (62% concentration) 21 Propionic aldehyde 41 'Water 13 Propyl propionate .2

In order to prove the general utility of withdrawing hydrogen from the zone of reaction when converting aldehydes, tests were conducted in which propionic. aldehyde was used in the charge and hydrogen withdrawn as formed by means of the porous thimble, as shown in the following example:

Example 28 In this example the same catalysts were employed as in 13 and the conditions of operation were the same. The charge consisted of 58 grams (1 mol.) of propionic, aldehyde and 18 grams (1 mol.) of water. During the treatment approximately 1 gram of hydrogen was removed from the reaction zone through the porous thimble. The liquid products of conversion resulting from this treatment analyzed as follows:

Grams N-propionic acid (80.5% concentration) 3'7 Propionic aldehyderfl 28 Water 9 Propyl propionate .3

In a manner similar to the treatment of acetic acid tests were conducted on the conversion of propionic aldehyde used in an excess of water, as shown in the following example:

Example 20,

In this treatment the conditions were the same as those in Example 23 with the'exception that in lieu of using 1 mol. ofwaterwith 1 mol. of propionic aldehyde, 3 mols. (54 grams) of water were used with 1 mol. (58 grams) of propionic aldehyde. 'During the operation 1 /2 grams, of

hydrogen were withdrawn through the porous thimble. Theliquidzproducts analyzed as follows: 5 v

- Grams N-propionic acid (58% concentration) 55 Propionic aldehyde 15 Water 40.5

, scribed are readily embodied in 'a simple process which operates very effectively and with relativearomatic acids, as is shown in the following example Example 3 50 grams of broken pumice, treated with the quantity of catalysts described in Example 1, were packed in a combustion tube, no porous thimble being used. Through this tube vapors of 1 mol. of benzaldehyde (106 grams) and 3 mols.

of water (54 grams) was passed and recycled. The temperature of the vapors was held at between 320 and 330 C. During the run 2 grams of hydrogen was vented from the cooler end of the dephlegmator. The liquid products of conversion were analyzed and found to correspond to a 10% yield of benzoic acid.

Similar runs were made with other aliphatic and aromatic aldehydes, such for example as formaldehyde, butylaldehyde and tolylaldehyde,

for the purpose of proving the general applicability of the process." In each instance a satisfactory yield of the corresponding acid was obtained.

It was found that the catalysts herein employed remain active over a long period of time, apparently maintained so byreason of the presence of the particular basic salts employed. However, it is to be observed that if desired a rejuvenation or revivification of the catalyst can be secured by admission of a small quantity of oxygen or air.

The diminution or driving down of the temperature for operation, especially below 270? C., makes for elimination of any carbon monoxide that may arise through the action of finely divided metals on Iacids. Indeed the absence of air and readily reducible oxides renders doubly secure the absence of carbon monoxide throughout the entire system. Thus is assured the prevention of poison effects known to result when carbon monoxide is condensed upon dehydrogenative catalysts.

It should be here notedthat the present invention comprehends no such function as that displayed by manganous acetate in its reducing capacity towards peracids and by the subsequent reduction of manganic compounds by aldehyde to a prior state for further duty. Such service is demanded when aldehydes contact with oxygen in order to keep down the concentration of peracids below; 1% (the lowermost limits permissible without explosion) The present invention furthermore comprehends no state of oxidation of organic salts, 'nor is there any rise in the state of oxidation in view of the total absence of oxygen or oxidizing material.

It is to be observed finally that, in view of the equilibrium conditions of the present process, the reverse action may be secured, that is the action of acid and hydrogen to give an aldehyde. Such results are readily obtainable but, owing to the high adsorption of the hydrogen by the catalytic mass, it is necessary to operate in an excess of hydrogen.

In line with the system of equilibria here set forth, it will be appreciated that it is possible to carry out the process described while employing other starting materials which are convertible by a preliminary treatment to the aldehyde. Thus it is possible to start with, for example, ethyl alcohol, and by proper treatment convert this to acetaldehyde and thence, by the described treatments, to acetic acid.

It will be appreciated that supporting materials other than pumice may be employed and that in general any siliceous and/or argillaceous mate rials having the characteristics of pumice may be used.

It will now be observed that an improved method 0! manufacturing organic acids has been described. The invention is conceived to reside broadly in the concept of preparing organic acids by hydration of the aldhehyde and the subsequent dehydrogenation of the intermediate compounds to the corresponding acids, under controlled conditions of temperature and catalysis. Hence, while certain specific examples have been given, it is to be understood that these are merely illustrative of the type of reaction herein involved, and are not to be considered definitive of the limits of the invention.

I claim:

1. A method of preparing organic acids which comprises contacting an aldehyde and water, in vapor phase, with a dehydrogenative catalyst and a directive catalytic base which catalytic base I organic acid.

3. A method of preparing organic acids which comprises contacting an aldehyde and water, below 300 degrees 0., with a dehydrogenatlve catalyst and a catalytic mass, which mass comprises a partially hydrolyzable salt of an amphoteric base and an organic acid, and conducting the operation, in the absence of substances which readily yield oxygen.

4. A method of preparing organic acids which comprises contacting an aldehyde and water vapor, at relatively low temperatures, hydrogenative catalyst and a catalytic mass comprising an incompletely hydrolyzable salt of an amphoteric base and an organic acid and conducting the operation in the absence of free oxygen.

5. A method of preparing organic acids which comprises contacting an aldehyde and water vapor, in the presence of a partially hydrolyzable salt of an amphoteric base and an organic acid and then contacting the mass with a dehydrogenative catalyst to produce the corresponding acid.

6. A method of preparing organic acids which comprises contacting an aldehyde and water with a deof producing organic acids which" 8. A method of producing organic acids which comprises passing an aldehyde and water, in vapor phase, at temperatures below 350 C. and in the absence of free oxygen, in contact with a salt of an amphoteric base and an organic acid," and a dehydrogenative catalyst; removing hydrogen formed from the zone of reaction, separating unconverted aldehyde from the reaction products and recycling such aldehyde for retreatment.

- 9. A method of producing aliphatic acids which comprises contacting an aliphatic aldehyde with a catalytic mass comprising a partially hydrolyzable salt of an amphoteric base and an organic acid and immediately dehydrogenating the hydrated aldehyde by contacting it with a dehydrogenative catalyst and in conducting the operation in one reaction zone and at temperatures between 250 and 280 C. I

10. A process of producing acetic acid which comprises passing a mixture of vapors of acetaldehyde and water over a catalytic mass including a dehydrogenative catalyst and a catalytic mass comprising a partially hydrolyzable salt of amphoteric base and an organic acid at temperatures approximately 275 C., continuously withdrawing hydrogen from the zone of reactionand continuously recycling unconverted acetaldehyde to the zone oi-reaction. P

11. A process of producing organic acids which comprises passing a mixture of an aldehyde vapor and water vapor over a catalytic mass including a dehydrogenative catalyst and partially hydrolyzable base ,and an organic acid, continuously withdrawing hydrogen from the zone of reaction and continuously recycling unconverted aldehydes to the reaction zone.

12. A catalytic mass for the conversion or organic aldehydes to their corresponding acids consisting of a hydroxy compound 01' an organic acid salt of a metal, such compound being partially hydrolyzable, together with a dehydrogenative agent and a carrier.

13. A method of preparing organic acids which 1 comprises contacting an aldehyde, in vapor phase,

with a hydroxy compound of organic acid salt of a metal, such compound being partially hydrolyzable, together with a dehydrogenative agent.

14. A process" of preparing organic acids which comprises contacting an aldehyde and water, in vapor phase, with a dehydrogenative catalyst and from the products of conversion andrecycling the remainder of said products of conversion.

17. A process of preparing organic acids which comprises contacting an aldehyde and water, in vapor phase, and below 350 C., with a dehydrogenative catalyst and a hydrative catalyst, the hydrative catalyst being in suflicient amount to hydrate substantially all of the aldehyde, and'the dehydrogenative catalyst being '--in suflicient amount to dehydrogenate the hydrated aldehyde. 18. A process of preparing organic acids from aldehydes which comprises contacting an aldehyde and water, in vapor phase, and below 350 0.,

with a catalytic mass including essentially a dehydrogenative catalyst and a hydrative catalyst,

and withdrawing hydrogen liberated during the 0 reaction from the reaction zone; WILLIAM'J. HALE; 

